Saturday, August 12, 2017

Construction practices going in reverse?

Recently, it seems that some politicians in the state of Florida are attempting to weaken the enhancements to building codes put in place following the massive disaster of Hurricane Andrew in 1992.  The hurricane revealed the vulnerability of homes built to low standards and the idea was to prepare for the inevitable return of a strong hurricane to Florida.  This current effort to weaken the codes is being led by the GOP, and it seems likely that the pressure to do so is coming from the homebuilders, who are essentially the only group that stands to gain from weakening the building codes.

Natural hazards like hurricanes and tornadoes have a tendency to fade from people's memories with time.  Immediately after a disaster, there's widespread support to do something to reduce the impact of the inevitable return of that hazard.  Sometimes, this is referred to as "closing the barn door after the horses have escaped."  Unfortunately, with the passage of time, the enthusiasm for preparing for the next hazard begins to fade.  Other ways to spend resources become a higher priority than hazard preparation.  In my experience (with tornadoes) the collective memory of disasters in communities virtually disappears within roughly 2 generations - about 60 years.  People live under the false assumption that what they've seen in their lifetimes in their location up to that point is pretty much how things will go for the rest of their lives.  Natural hazards are rare in any one place, but it's only a matter of time before they strike again.

For people who experience for themselves the horrors of a natural disaster, the memories often are still vivid decades later.  But survivors move elsewhere, older victims die, and people who move in afterwards generally haven't experienced with the survivors and victims experienced.  In our reanalysis of the Tri-State tornado, we found that the stories told by survivors are widely regarded locally as unreliable and exaggerated, whereas in our interviews with survivors, many of those stories could be corroborated by independent evidence!  I suppose it's something of an "inconvenient truth" to learn that the natural hazards can be so devastating in the place where you live.  The unpleasant reality is that if an event has happened at least once in some area, there's no reason to believe it won't happen again.  Low probability does not equal zero probability!

Interestingly, over much of Europe, building construction standards are substantially higher than in most of the USA.  This can be seen directly in the degree of damage when tornadoes in Europe hit human structures; equivalently strong tornadoes in Europe do less damage than in the USA!

Think about the relationship between construction practices and the lethality of, say, a violent tornado or a powerful hurricane.  What's responsible for most of the fatalities in a tornado?  It's flying debris ... broken 2x4s, shingles, tree branches, sometimes even cars!  There's a kind of mythology that says there's no point in strengthening building that might be hit by a tornado, because no affordable construction can withstand a tornado, right?  No, that couldn't be more wrong!

The costs to enhance structural integrity over the existing code standard of 90 mph in most of the USA, when amortized over the life of a 30-year mortgage is pretty small.  What the builders don't like is that it takes more time to build a better home, and that is what reduces their profit.  If they can build 10 shoddy homes in the time it takes to build 6 well-constructed homes, that's where they make their gains.

First of all, even in a violent tornado (i.e., one rated EF-4 or EF-5 on the enhanced Fujita scale), the most violent winds are experienced in only a small fraction of the total damage path of a tornado - typically less than 10%.  Those areas experiencing EF-3 winds or less would experience considerably less damage if their structural integrity would be enhanced over what is typical construction in the US.  Decreasing damage means less flying debris.  Shoddy construction increases the potential death toll, as well as increasing the destruction.  In most of the US, the building code requirements are such that the building should experience no structural damage at windspeeds of 90 mph or less.  The fact is that most wood frame homes built in the US are built below the code requirements, sometimes far below.  Code enforcement is pretty often woefully inadequate.  The cost of a home isn't a very good indicator of construction quality, unfortunately.  Local communities often give in to pressure from developers and homebuilders, passing laws to allow "exemptions" from code-prescribed building practices. 

When subjected to powerful winds, structural failures begin with the weakest component in the structure - often the attachments of the roof to the walls and/or the attachment of the walls to the foundation.  A 90-mph wind speed puts a tornado with that as its peak wind toward the bottom of EF-1.  Thus, even a weak tornado can cause structural damage under this building standard.  Once structural failure begins, further failures are likely - a home can be "unzipped" starting from one initial weak point.  Further, a 90-mph wind can push a home off its foundation when the walls are poorly attached - we call such homes "sliders" because they can be slid off their foundation and then utterly collapse.  Such a home can be totally wrecked by a 90-mph wind!

The building code requirements in Miami under the enhancements after Hurricane Andrew are on the order of 120 mph before structural damage will occur.  That wind speed falls about in the middle of the EF-2 category, such that much of the area experiencing EF-2 winds will have only marginal structural damage.  The area of EF-2 or less wind speed includes the majority of the damage path in even a violent tornado.  Even EF-3 winds will produce less damage with the enhanced code.

For Florida to weaken its building codes is to return to a time of lowered resistance to damage, likely resulting in more casualties.  That some of the politicians in Florida are seeking legislation to lower the standards is an indicator that the homebuilders are using their political influence to lobby the state government for the benefit of their profits.  Who else benefits from lowering the construction standards in Florida?  Weakening construction standards is an idea that should be nipped at the bud!

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